Chapter 2 Literature Review Page 17 CHAPTER-2 LITERATURE REVIEW Overview The study of the wear behaviour of the particle reinforced aluminium matrix composite developed using different fabrication techniques done by many researchers is discussed in this chapter. Special emphasis is given on the studies of the development of particle reinforced aluminium matrix composite by stir casting process as the present work is based on this process. The study mainly focuses on the physical properties, especially wear resistance of the composites. The work of the thesis is planned with the aim keeping in view the gap in the study, which is presented in the last section of this chapter.
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Chapter 2 Literature Review Page 17
CHAPTER-2
LITERATURE REVIEW
Overview
The study of the wear behaviour of the particle reinforced aluminium matrix composite
developed using different fabrication techniques done by many researchers is discussed in this
chapter. Special emphasis is given on the studies of the development of particle reinforced
aluminium matrix composite by stir casting process as the present work is based on this process.
The study mainly focuses on the physical properties, especially wear resistance of the
composites. The work of the thesis is planned with the aim keeping in view the gap in the study,
which is presented in the last section of this chapter.
Chapter 2 Literature Review Page 18
2.1 Introduction
Three decades of intensive materials research have provided a wealth of new scientific
innovation to synthesize special materials with enhanced efficiency with low manufacturing cost
to fulfill the long pending demands of the engineering sector. A new system of materials
containing hard particulates embedded in a metal matrix have exhibited superior operating
performance and improved tribological behaviors.Among MMCs, aluminium alloy based
composites had shown the significant improvement in the mechanical, thermal, electrical and
wear properties to cater the demand of the industries. Al alloys are termed as versatile materials
to be used for numerous engineering applications because of its better machining, joining and
processability. In addition to this, low cost, increased strength to weight ratio and other
environmental friendly characteristics of Al alloys make them a preferable material in
engineering applications [1].
Among the aluminium alloys, Al-Si alloy is well known casting alloy having high wear
resistance, low thermal expansion coefficient, good corrosion resistance with improved
mechanical properties over a wide range of temperatures. The grain refiner elements modify the
Si morphology from coarse to lamellar (fine), thus enhancing the mechanical properties [2].
Different researcher developed numerous composite materials by using different type of matrix,
reinforcement size, shape and volume as well as suitable processing technique depending upon
the requirement and application. In order to achieve the optimum properties of the metal matrix
composite, the distribution of the second phase in the matrix alloy must be uniform, and the
wettability or bonding between these substances should be optimized. [3].
Rao and Das [4] prepared cast aluminium-alumina composites by incorporating alumina particles
while stirring the molten alloy with an impeller. The particles were added in the molten metal
during mixing and thus the process of stir casting emerged. In addition to this mixing of non-
wetting particles into alloys was promoted by addition of alloying elements such as magnesium
during the composite synthesis. Prasad et al. [5] began the practice of introducing particles to
semi-solid alloys at a temperature between those of the solids and the liquids for the alloy.
Wear behavior of ceramic particle(s) reinforced AMCs has been studied by several workers. It
includes reinforcement of SiC, Al2O3, TiC, C, B4C, fly ash, TiB2, Al3Zr etc. either singly or in
hybrid way. The breif summary of their study has been given in table 2.1.
Chapter 2 Literature Review Page 19
Table 2.1: Tabulated summary of outcomes of various investigators on the development and wear behavior study of ceramic particles reinforced AMCs.
Investigator [Year]
Materials [Matrix/Reinfor-
cement]
Process Parameter Investigated
Outcomes
Alpas and
Zhang(1992) [6]
Aluminium alloy
with 10 and 20%
SiC
Stir casting Wear rate over a load
of1-150N at different
sliding velocities
At low load, corresponding to stresses lower than the particle fracture
strength, SiC particles were the load bearing constituents and their abrasive
action successfully transferred the rich iron layer on to the contact surface.
However, wear rate of the composite was found to be lower than the
unreinforced alloy in this regime.
Above a critical load, the SiC particles got fractured and the delamination
wear was due to de-cohesion of SiC-matrix interfaces. The wear behaviour of
the composite was similar to the unreinforced matrix alloy in this regime.
With the continuous increase of load, there was an abrupt increase in wear
rate by a factor of 100. The SiC reinforcement was proved to be very
effective in suppressing the transition to severe wear regime.
Martin et al.
(1996) [7]
2618 Al alloy
reinforced with 15
vol.% SiC
Stir casting Wear resistance in the
temperature range 20–
200 °C
The addition of the SiC particulates improved the wear resistance by a factor
of two in the mild wear region, and the transition temperature was raised by
approx. 50 °C. This higher transition temperature was due to the retention of
the mechanical properties in the composite at elevated temperature.
Heat treatments (either natural or artificial aging) did not modify
substantially the wear resistance of either the composite or the unreinforced
alloy.
Wilson and Alpas
(1996) [8]
A 356 Al alloy
reinforced 20% of
Al2O3, SiC and
Stir Casting High temperature dry
sliding wear resistance
Mild to severe wear delay was observed in the composites with the addition
of Al2O3 and SiC but a hybrid A356 Al composite containing SiC and
graphite remained in a mild wear regime even at the highest test temperature
Chapter 2 Literature Review Page 20
Graphite of 460°C.
The absence of severe wear phenomena in this composite contributes to the
inhibition of comminution and fracture by graphite entrained in the surface
tribolayer.
Yu et al.
(1997) [9]
6061 aluminium
alloy with 5 & 10%
SiC whiskers or SiC
particulates
High pressure
infiltration
Wear behaviour The wear rate decreased with the increase in the applied load.
Above a critical applied load, rapid increase in the wear rate led to the
transitions in wear mechanism.
The critical load decreased with temperature for both the composites.
Straffelini et al.
(1997) [10]
6061 Al alloy
reinforced with 20
Vol.% Al2O3
particles
Hot Extrusion Wear behaviour as a
function of load
The wear mechanism was abrasive and oxidative at the low loads. All
materials have shown a transition to a severe form of wear with a massive
removal of wear debris for very high applied loads of 200 N accompanied by
the plastic deformation of the surface material.
The addition of Al2O3 postponed the transition to severe wear at higher loads,
thus effectively improved the sliding wear behaviour of the composite.
Shipway et al.
(1998) [11]
Aluminium
reinforced with 10
and 20% TiC
Improved Stir
casting
MMMMM
Wear behaviour as a
function of load and
particle volume fraction
Particle additions have reduced the wear rate of the composites and hence
delayed the transition with load from low wear coefficients to high wear
coefficients.
The addition of higher amount of reinforcement resulted in a reduction in
wear rate and further led to the retardation of the load at which wear
coefficient increases.
Auida et al.
(1999) [12]
Aluminium alloy
A356 with 5%,10%
and 15% vol. SiC
Stir casting Porosity content at
different speeds
Low speed of 100rpm tempted the clustered particles to enhance the porosity
formation.
Uniform distribution of particles was observed at the speed of 200rpm with
less porosity. Higher porosity due to the entrapment of gas occurred at
500rpm.
Chapter 2 Literature Review Page 21
The higher content of silicon carbide increased the porosity volume.
J. Hasim
(2001) [13]
Aluminium alloy
A359 with 5-25%
vol. SiC
Two step Stir
Casting
Microstructure,
Hardness, Tensile
strength
Successful fabrication of aluminium matrix composite by using the stir
casting method has added a new dimension to the processing of cast
composites.
The porosity level was reduced by preheating the ceramic particles to burn
off the any moisture.
Microstructural observation revealed that the reduction in grain size due to
the stirring action of the slurry strengthen the composite more as compared
with the unreinforced alloy.
Bindumadhavan
et al. (2001) [14]
Al alloy(356)
reinforced with 15%
SiC small and large
particle sizes
Stir casting Hardness, Wear
resistance
The hardness of the composite increased with the SiCp content which also
reduced the wear loss.
For the same total volume fraction of SiC reinforcement the composite with
small sized particles displayed better wear resistance as compared to the large
sized particles composite.
Dual Particle Sized (DPS) composites have potential for their material
properties to be suitably altered to meet different engineering requirements
by a suitable choice of particle sizes.
Riahi and Alpas
( 2001) [15]
Graphitic aluminium
reinforced with 10%
SiC and 5% Al2O3
Stir casting The role played by the
tribolayers
Three main wear regimes, namely ultra-mild, mild and severe wear were
determined.
In the mild wear regimes, the protective tribolayers was formed at all the
sliding speeds and load.
Tribolayers safeguarded sub surface of the region and also delayed the
transition from mild to severe wear.
The graphitic composites was developed for cylinder liner applications in
cast aluminium engine blocks.
Chapter 2 Literature Review Page 22
Jun et al.
(2004) [16]
Al–12Si alloy
reinforced 12%
Al2O3 and 4%
carbon short fibers
Squeeze-
infiltration
The effects of applied
load and reinforcing
fibre on wear properties
Carbon fibre was more efficient in improving wear resistance of the hybrid
composites at high applied load.
When applied load was below the critical load, dominant wear mechanisms
were ploughing grooves and delamination.
The dominant wear mechanisms shifted to severe wear when the applied load
exceeds the critical load.
Kok-.K
(2005) [17]
Aluminium alloy
reinforced with three
different sizes and
weight fractions of
Al2O3particles up to
30 wt.%
Vortex method
and subsequent
applied pressure
Mechanical properties
e.g.
Hardness , Tensile
strength, Porosity
The density measurements have shown that the samples contained little
porosity, and the amount of porosity in the composites increased with
increasing weight fraction and decreasing size of particles.
The hardness and the tensile strength of the composites increased with
decreasing size and increasing weight fraction of particles.
Vencl et al.
(2006) [18]
Al alloy reinforced
with 3 wt.% Al2O3
Compo-casting Hardness and Wear
resistance at high load
Improvement of wear resistance for the composite material with 3 wt. %
Al2O3 reinforcement was significant for specific load up to 1 MPa.
Adhesive wear was a predominant mechanism of wear followed by plastic
deformation with increase of specific load.
Han Jian-min et
al. (2006) [19]
Al alloy (A356) with
10% and 20% SiC
vol. particles
Improved Stir
casting
Microstructures of the
cast composites
Microstructure of the cast composites revealed three phases of the
composites e.g. α-Al, eutectic structures and SiC particles be located
predominantly in the inter-dendritic regions.
The growth of α-Al nuclei led to enrichment of SiC in the melt around the
particles. The interface formation between SiC and the matrix was confirmed
by the interface reaction products such as Al4C3 which was also detected
Chapter 2 Literature Review Page 23
experimentally.
An improved stir casting process is established for fabricating SiCp/A356
composites with good mechanical properties and less defects.
Mondal et al.
(2006) [20]
Al–Si alloy (ADC-
12) with SiC
Stir casting Microstructure, Wear
behaviour
Addition of ceramic reinforcement such as SiC particles improved the wear
resistance of the alloy.
Transition in wear mechanism from microcutting/ploughing dominated to
micro-cracking and -fracturing dominated wear took place when abrasive
size increased from 100 to 120 mm.
The wear resistance increased linearly with increase in SiC content and
decreased with increase in reinforcement size.
Pathak et al.
(2006) [21]
Aluminium- alloy
reinforced with
0.6,1.5 and 2.2%
SiC particles
Stir casting Strength, Hardness,
Wear resistance
coefficient of friction
The silicon carbide particles dispersed in the grain boundary regions and
fragmented dendrites in the synthesized SiC particles aluminium-silicon alloy
was observed.
Increased hardness of the matrix alloys with the incorporation of silicon
carbide powder also improved the wear resistance of composite under dry
sliding.
The thick oxidative layers in the composite with higher amount of silicon
carbide safeguarded the matrix even under high loading conditions.
Composite having higher amount of SiC possessed lower frictional resistance
than to lower amount of SiC composite.
Uyyurua et al.
(2007) [22]
Al–Si/15 and 20%
SiCp
Stir casting Wear rate , Friction
coefficient with the
variation of applied load
and sliding speed
With increase in the applied normal load, the wear rate is observed to
increase whereas the friction coefficient decreases.
The wear rate and friction coefficients are observed to vary proportionally
with the sliding speed. During the wear tests, formation of a protective tribo-
layer is observed, which plays a significant role in determining the wear
Chapter 2 Literature Review Page 24
behaviour of the composite apart from acting as a source of wear debris.
Rodriguez et al.
(2007) [23]
Al-8090 with 15 vol.
% SiCp
Spray co-
deposition
Wear behaviour at
different pressures and
temperatures
At a transition temperature, the wear rate changed from mild to severe wear
for both the composites. The SiC reinforcement addition successfully shifted
the transition temperature to higher values which were also dependant on
pressure.
It has been also observed that the presence of mechanically mixed layers on
the wear surface with varying morphology and thickness seemed to be a key
factor controlling the mild wear of these materials.
Prabu et al.
(2008) [24]
A384 Aluminium
alloy with 10% SiC
Stir casting Stirring speed, Stirring
time,
Hardness
Microstructure analysis clearly indicated that at low stirring speed of 500rpm
and stirring time clustering was the predominant phenomenon.
At high stirring speed of 700rpm the increase of porosity was dominant and
both are detrimental to the mechanical properties of the composite.
The processing parameters standardization at a speed of 600rpm with 10 min
was done to achieve defect free composite with uniform hardness.
Tang et al.
(2008) [25]
Al-5083 matrices
reinforced with 5 and
10 wt.% B4C
particles.
Hot
isostatic
pressing (HIP)
Coefficient of friction,
Wear rate at different
sliding speeds at the
variable loads
The composite prepared with 10 wt.% B4C yielded 40% lower wear rate
than that of the composite with 5 wt.% B4C under the same test conditions.
This experimental result indicated a significant effect of the B4C particles on
enhancing the wear resistance of these composites.
The change in the wear mechanism from abrasive wear to adhesive wear was
attributed to the change in coefficient of friction.
Sudarshan and
Surappa
(2008) [26]
A356-Al composites
containing 6 and 12
Vol.% fly ash
particles
Stir casting Mechanical properties Increased volume percentage of the reinforcement increased the porosity due
to the long processing time which consequently led to increase in pickup of
hydrogen from the atmosphere.
The results showed considerable increase in both the bulk hardness and micro
hardness due to addition of fly ash.
Chapter 2 Literature Review Page 25
The composite with 6% fly ash exhibited higher compressive strength
compared to 12 Vol.% fly ash reinforced composite.
The prepared A356 Al fly ash metal matrix composite displayed superior
damping characteristics compared to unreinforced alloy at ambient
temperature.
Natarajan et al.
(2009) [27]
Aluminium
reinforced 5 and 10%
TiB2
In-situ Wear behaviour at
elevated temperatures
The hardness and wear resistance of TiB2 reinforced composite was higher
than the unreinforced matrix alloy at all test temperature and also increased
with the increase in amount of TiB2 which enhanced the load carrying
capacity of the composite.
The wear mechanism of the composites changed from abrasive wear to
oxidative wear with the rise of temperature.
At high temperature above 200oC, severe adhesive wear occurs when crack
propagation was predominant factor.
Rao and Das
(2010) [28]
Al-Zn Mg (7009)
alloy10,15
and 25wt.%
SiC particle
Stir casting Effect of heat treatment
on the sliding wear with
applied load and sliding
speed
The uniform distribution of SiC particles in aluminium alloy matrix was
observed and the dendrites of Al and precipitates along the inter-dendritic
regions were present.
The maximum hardness was obtained at the peak aging 6h of heat treatment
and wear rate increased with increasing sliding speed and load.
Addition of SiC particle increased the seizure pressure and temperature
.
Kaur et al.
(2010) [29]
SiC reinforced Al-Si
along with the SiC
5% and 10% addition
Spray forming Wear rate under different
loading conditions and at
various temperatures
The change in wear mechanism was observed with the increase in applied
load.
The SiC reinforced composites exhibited better wear resistant than
unreinforced alloy even at higher loads due to the oxidative-cum-adhesive
wear mechanism.
Chapter 2 Literature Review Page 26
Kumar et al.
(2010) [30]
AA7075Al
l5- 25% SiC
Powder
metallurgy
Hardness, Abrasive wear
behaviour with different
particle sizes using
mathematical model the
analysis of variance
(ANOVA)
Hardness of the composite increased with the SiC addition and micrographs
showed uniform distribution of the SiC particles.
The abrasive wear behaviour clearly indicated the increase in wear resistance
as SiC acted as a load-supporting element.
Composites with larger reinforcement size and high volume fraction
displayed improved abrasive wear resistance as compared to other
combinations.
At high load, particle pull out was the dominant wear mechanism in
composites with finer SiCp, whereas particle fracture and wearing of SiCp
was the predominant in composites with coarser SiCp.
Sreenivasan et al.
(2011) [31]
Al 6061 alloy
reinforced with 5,10
,15%TiB2
Stir casting Microstructure and Wear
behaviour at different
loads and speeds
The microstructure revealed the segregation of TiB2 particles in the inter-
dendritic region as rejected by the α-aluminium dendrites.
Wear rate decreased with increasing the content of TiB2 on the other hand it
increased with the applied load.
Abrasive wear was demonstrated at low loads, whereas, in the case of higher
applied loads, delamination wear was dominant.
Rao and Das
(2011) [32]
Aluminium alloy
with 10 and 25% SiC
Stir casting
Inter-metallic phases,
Coefficient of friction,
Seizure resistance
The formation of inter-metallic phases such as Al2CuMg and Mg2Cu6Al5
were found in Al-Cu-Mg alloy in as cast condition. The surface temperature
and coefficient of friction significantly increased with increase in the applied
pressure.
At lower applied pressure, formation of continuous grooves, MML and some
damaged regions were seen. At high pressure, in seizure condition the wear
was characterized by the formation of parallel lips, destruction of MML
along the sliding direction.
The seizure resistance was found to improve with the amount of SiCp.
Chapter 2 Literature Review Page 27
Reddappa et al.
(2011) [33]
Al-6061 reinforced
with 2, 6, 10 and
15% beryl
composites
Stir casting Hardness, Wear rate ,
Friction coefficient with
the variation of applied
load
High friction coefficient was observed due to the strong interlocking of the
rough surfaces in contact during the initial stages of sliding,.
Abrasive wear was dominant in the steady state and a transfer film formed on
the surface reduced the wear rate.
The increase of load led to a significant increase of the wear rate. As the load
increased from lower to higher values the morphology of the worn surface
gradually changed from the scratches to distinct grooves and flake craters
.
Radhika et al.
(2011)[34]
Aluminium alloy
(Al-Si 10 %)
reinforced with
alumina (9%) and
graphite (3%)
Stir Casting Wear rate prediction
using Taguchi design
The sliding speed, applied load and sliding distance increased the wear rate.
Incorporation of reinforcement increased the wear resistance of the
composite by forming a protective layer between pin and counter face.
Comparison between the experimental and the computed values confirmed
that Taguchi design was successfully used to predict the tribological
behaviour of composite.
Toptan et al.
(2012) [35]
Al alloy reinforced
with 15 and 19% B4C
Squeeze casting
route at low
vacuum.
Micro-structural features
and the reciprocal dry
sliding wear behaviour
The homogeneous distribution of the B4C particle with decreased porosity
was attributed to the addition of Titanium containing flux which promoted
the wetting between B4C and liquid aluminium metal.
ANOVA analysis showed strongest statistical and physical significance on
the wear rate which was found to increase with volume fraction, load and
sliding distance and decreased with sliding velocity.
The examinations of the worn surfaces confirmed that wear mechanism was a
combination of adhesive, abrasive and delamination wear.
Chapter 2 Literature Review Page 28
Kumar et al.
(2012) [36]
Al6061 reinforced
with 2- 6 wt.% SiC
Stir casting
Density, Hardness,
Tensile strength,
Wear properties
Hardness, density, tensile strength increased with the filler content.
The wear resistance of the composite was higher than that of the base alloy.
The composite with 6 wt.% reinforcement exhibited superior mechanical and
tribological properties.
Lakhvir et al.
(2012) [37]
Al alloy with
3, 6 and 9% Al2O3
particles
Stir casting Effect of different input
processing parameters
i.e. particle size, wt% of
reinforcement, stirring
time wt. %
Increasing trend in hardness, tensile strength and impact strength was
observed with higher weight percentage.
All these mechanical properties displayed upward trend with increase in
weight %, stirring time and decrease in particle size of the reinforcement.
Zhu et al.
(2012) [38]
Al alloy reinforced
with 20 and 30%
alpha Al2O3 and
Al3Zr particles
In-situ High temperature wear
behaviour
With the rise in temperature due to sliding, the work hardening occurred on
the wear surface which enhanced the wear resistance of the composite.
Recrystallization taking place at the wear surface during the dry sliding have
resulted in the decrease in the hardness of the wear surface thus increased the
wear loss.
Nagaral et al.
(2013) [39]
6061 Al alloy
reinforced with 3,6
and 9% Al2O3
particles
Stir casting Hardness, Tensile and
Yield Strength
Hardness, tensile and yield strength was observed to increase with the weight
% of reinforcement.
The optical micrographs revealed uniform distribution of particles and
microstructure contains the primary α - Al dendrites and eutectic silicon with
Al2O3 particles separated at inter-dendritic regions.
The composite demonstrated improved wear resistance due to incorporation
of hard Al2O3 particles in the 6061 Al alloy which restricted the ploughing
action of the hard steel counterparts.
Shivaprakash et
al. (2013) [40]
2.5%-15% flyash
reinforced AA2024
Stir casting Hardness ,Wear
mechanism by
performing the wear test
The increase of fly ash content increased the matrix hardness which in turn
enhanced the wear resistance of the composite as compared to the
unreinforced alloy.
Chapter 2 Literature Review Page 29
by varying the speeds
and by applying different
normal loads
The filler volume was optimized between 23 to 35% which can provide the
maximum wear resistance to the composite.
Uthaya kumar et
al.
(2013) [41]
Al alloy with 5,10
and 15% SiC and
B4C
Stir Casting Coefficient of friction,
Wear resistance
The B4C particles enhanced the production of rich tribo oxide layer by
forming boron oxide which has reduced the progress of wear and coefficient
of friction.
At high loads and sliding velocities plastic deformation was the operating
wear mechanism accompanied by the melt wear due to high order of local
stress prevailing at the condition.
Boopathi et al.
(2013) [42]
Aluminium with 15%
SiC- fly ash
Stir Casting Physical and Mechanical
properties
The incorporation of reinforced particles decreased the density of the
composite.
Increase in area fraction of reinforcement in matrix resulted in the
improvement of hardness, tensile strength and the yield strength.
Increased percentage addition of SiC and fly ash decreased the rate
elongation of the hybrid composite.
Altinkok et al.
(2013) [43]
Al alloy reinforced
with 10% of
Al2O3/SiC
Stir Casting Micro-structural studies
and
Wear behaviour at high
temperatures
Hybrid particle distribution within the matrix increased the wear resistance.
Fine Al2O3 particles were well distributed in the inter-particles spacing of
coarse SiC particles within the matrix which hardened the matrix and
decreased the wear rate.
The coefficient of friction of a fine hybrid particle size MMCs was lower
than that of a coarse particle size MMCs at room temperature.
Baskaran et al.
(2014) [44]
Al-7075 alloy with 4
and 8% of TiC
Reactive in-situ
casting
Microstructural studies
Wear behaviour
SEM analysis showed that TiC particles were uniformly distributed along
the grain boundaries.
Chapter 2 Literature Review Page 30
particulate
reinforcement
Incorporation of 4% TiC improved the maximum wear resistance of the
composite as compared to 8%TiC composite.
Show et al.
(2014) [45]
635 Al alloy with
4% (Al2O3+SiC)
hybrid reinforcement
Stir Casting Wear behaviour at
different loads
• At lower load, the dominant wear mechanism involves adhesion and micro
cutting abrasion.
At higher loads abrasive wear involving micro cutting and micro-ploughing
with the oxide formation which was the main cause of wear damage.
• Hybrid composite (2 Vol% Al2O3+2 Vol% SiC) exhibited the best wear
resistance due to massive clusters which resisted the abrasive action.
Chapter 2 Literature Review Page 31
2.2 Mineral Reinforced Aluminium Composites
Since the present work deals with the reinforcement of rutile mineral so the details of mineral
reinforced composite are described below. In order to reduce the cost of the composites,
reinforcement of naturally occurring minerals is now being done. Though the work is in the
preliminary stage but offers high potential as these reinforcement are easily available with low
cost. Moreover, there is no hazardous material involved in it. Waste composites can be easily
recycled also. Since the present work is also on less studied rutile reinforced composite, so a
detailed study of the minerals reinforced composite is presented here. The properties of cast
aluminium alloy-sillimanite particle composite prepared by stir casting were studied by Singh et
al. [46]. The microstructure of the composites showed reasonably uniform distribution of
sillimanite particles and good mechanical bonding with the matrix alloy. The hardness and wear
resistance of the composite were found to be significantly higher than those of the base alloy. It
was found that aluminium-sillimanite composite can be used as a wear resistant material in place
of aluminium alloy. Singh et al. [47] also studied the two body abrasive wear behaviour of the
cast aluminium alloy reinforced with 10 wt.% sillimanite. They studied the wear behavior of stir
cast AMCs containing coarse and fine size sillimanite particles at different loads and for different
sliding distances. Wear rate of the composites and the matrix alloy increased with the increase in
applied load and abrasive size. The greater fracturing tendency and decohesion of ceramic
reinforcements due to combined effect of higher load and coarser abrasives led to the formation
of wider and deeper wear grooves. Wear resistance of the composite was superior to that of
matrix alloy for finer size abrasives, whereas the trend reversed for coarser size abrasives.
Ranganath et al. [48] studied the dry sliding wear behaviour of garnet reinforced zinc/aluminium
metal matrix composites. The results indicated the decrease in wear rates of the composites with
the increase in garnet content. Increment in wear rate was observed with increasing the applied
load and sliding speed. Sharma et al. [49] investigated the tribological behaviour of Al 6061-
garnet particulate composite prepared by the liquid metallurgical technique. The hardness and
wear resistance of the composite was found to increase with increasing content of garnet
particulate. It was observed that mechanically mixed layer (MML) was responsible for the
decrease in wear rate and coefficient of friction which improves the tribological behaviour of the
Al-6061 to a greater extent with the addition of garnet reinforcement.
Chapter 2 Literature Review Page 32
Chaudhary et al. [50] prepared Al-2Mg-11TiO2 composites through spray forming and stir
casting technique and compared the frictional and wear behaviour of the composites. They
observed the reduction in wear rate as compared to the base alloy when tested under the similar
conditions. Higher micro hardness at the interface as compared to the matrix reflects good
interfacial bonding. They also found that, addition of TiO2 particles in the alloy change the wear
mechanism from purely adhesive to mixed mode of oxidative and abrasive wear. The size of the
wear debris increased with the increase in load due to the increased size of the width of grooves.
The pull out of TiO2 particles during wear caused abrasion on the matrix surface resulting in
severe deformation of particles and platelets. The change from mild to severe wear was delayed
in the composite as compared to the alloy with the increase of load.
Hamid et al. [51] prepared a light weight TiO2 reinforced composite by dispersing titanium
dioxide (TiO2) particles in the molten aluminium. The influence of both reinforcing particles and
porosity contents on the wear and friction of in situ cast composites were evaluated. It was
observed that wear rate and coefficient of friction of the in-situ cast composite decreased with
the increasing load and the porosity content and also found to increase with the increasing the
TiO2 content.
Chaudhary et al. [52] prepared the Al-2Mg-7TiO2 composite using spray forming technique
because of its scope of forming near-net shape product in a single step at high casting rates.
Microstructural observations revealed better particles-matrix bonding and higher degree of
uniformity in the distribution of rutile particles in the matrix of spray formed composite vis-à-vis
stir cast composite. Hardness of the spray formed composites was found to be greater than the
stir cast composites due to lower amount of porosity with refined grains in spray formed
composite. Hardness of the composites increased appreciably with the degree of mechanical
working. The ultimate tensile strength of spray formed composite was greater than the stir cast
composite, but elongation showed lower values due to refined grains in spray formed
composites.
Hemanth et al. [53] used Taguchi technique for the simultaneous optimization of tribological
parameters in metal matrix composite. Aluminium metal matrix composite (Al-Cu-Mg) alloy
reinforced with 6wt % of titanium dioxide was prepared using stir casting method. Dry sliding
wear and frictional force of the composite material under different loads and sliding velocities
revealed the improved wear behaviour of the composite.
Chapter 2 Literature Review Page 33
Das et al. [54] used stir casting route for incorporating zircon sand particles of different sizes and
amounts in Al- 4.5Cu alloy melt. Scanning electron micrographs had shown that the coarser
particles are more spherical in shape compared to the finer ones. Due to the high coefficient of
thermal expansion of the particles as compared to the matrix, the solidification in the vicinity of
larger size of the reinforced zircon particles was delayed which caused more refinement in grain
morphology. XRD pattern of synthesized composites showed the presence of Al, CuAl2 and
zircon. Wear resistance improved significantly with the addition of zircon sand particles in Al-
4.5Cu alloy. The abrasion resistance of the composite increased with the increasing amount of
particle and decreasing particle size.
Mazahery et al. [55] studied the abrasive wear behaviour of ZrSiO4 reinforced aluminium matrix
composite (AMCs). The uniformity in the distribution of the particles within the matrix was the
salient micro-structural feature which influenced the properties of the particulate AMCs. They
found that, superior wear resistance was offered by the composite material as compared to the
alloy, irrespective of the applied load and zircon particle volume fraction. At the critical load,
abrupt increase in wear rate was attributed to high frictional heating thus the localized adhesion
and softening of the surface with counter surface. The results were consistent with the rule that in
general, alloy reinforced with minerals acquire more hardness and display better wear and
abrasive resistance.
Panwar et al. [56] studied the wear behaviour of zircon sand reinforced LM13 alloy composites
at elevated temperatures. The four composites with 5, 10, 15 and 20 wt.% of zircon
reinforcement were developed by stir casting route. XRD pattern of the composites revealed
good bonding between the LM13 alloy and zircon sand particles, which was attributed to the
formation of Al2SiO5 phase at interface due to the reaction of zircon sand and LM13 alloy during
casting. Zircon sand particles enhance the hardness and wear resistance at a particular load and
lowered coefficient of thermal expansion. Composites with more than 10 wt.% of reinforcement
show better wear resistance at higher temperature. Abrupt change in the wear rate in the wear
graphs at different temperatures marked as the transition temperature, because of the softening of
the matrix. Transition temperature was observed to increase with increase in the amount of
reinforcement. Microstructural analysis of wear tracks and debris revealed that both adhesive and
abrasive wear mechanisms were dominant in determining the wear of the composites.
Chapter 2 Literature Review Page 34
Okafor and Algbodfon [57] studied the properties of Al-4.5 Cu/ZrSiO4 particulate cast composite
with 5-25 wt.% the variation in ZrSiO4. Microstructural examination of the composite revealed
the existence of interfacial zone between the metal matrix and the reinforcement material. The
interfacial analysis regarding the thermal, electrical and mechanical properties of the composite
was the important factor while designing the MMC for a particular task. From the results, it was
concluded that the addition of ZrSiO4 particles using Al-4.5Cu alloy increased both the strength
and hardness and also an overall reduction in toughness and density. The addition of zircon sand
particles also increased the apparent porosity of the composites. These observations led to the
possibilities that the Al-4.5Cu/15wt.% ZrSiO4 composite could be a better material for